Why are ashes sprinkled on the head in some places?

[Joab_Anias]

I noticed administering ashes on top of the head in Rome instead of on the forehead and have never seen this here in the States. Why is this?

 

[Michelle_Arnold]

Sprinkling ashes on the crown of the head recalls the biblical method of putting on sackcloth and ashes as a sign of penance:

Now on the twenty-fourth day of this month the people of Israel were assembled with fasting and in sackcloth, and with earth upon their heads (Neh 9:1).

The American method of smearing ashes on the forehead, usually in the sign of the cross, allows the ashes to be visible to others so that the communal penitential nature of the day might be more readily seen.